Spirally and/or radially serrated superhard cutter

ABSTRACT

A cutter for use with a drill bit includes: a substrate for mounting in a pocket of the drill bit and made from a cermet material; and a cutting table made from a polycrystalline superhard material, mounted to the substrate at an interface, having a working face opposite from the interface, and having at least four serrations formed in the working face and a side thereof. Each serration has a pair of base edges and an apical edge extending above the base edges at the side of the cutting table. Each edge extends radially or spirally from the side of the cutting table to a central portion of the working face. The edges all converge at the center of the working face.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure generally relates to a spirally and/or radially serrated superhard cutter.

Description of the Related Art

U.S. Pat. No. 4,984,642 discloses a composite tool including a sintered metal carbide support and a polycrystalline diamond active part having an inner surface of metallurgical connection to the support and an outwardly facing working surface. The working surface comprises corrugations which are substantially parallel to one another and form successive projecting zones and hollow zone on at least a part of the working surface. The composite tool is in particularly intended for drilling to a great depth, such as drilling oil wells.

U.S. Pat. No. 5,848,657 discloses a domed polycrystalline diamond cutting element wherein a hemispherical diamond layer is bonded to a tungsten carbide substrate, commonly referred to as a tungsten carbide stud. The cutting element includes a metal carbide stud having a proximal end adapted to be placed into a drill bit and a distal end portion. A layer of cutting polycrystalline abrasive material disposed over said distal end portion such that an annulus of metal carbide adjacent and above said drill bit is not covered by said abrasive material layer. The geometry of the diamond cutting element provides control of interfacial stresses and reduces fabrication costs. The diamond cutting element may contain a pattern of ridges or bumps integrally formed in the abrasive layer which ridges are designed to cause high localized stresses in the rock, thus starting a crack. By initiating cracks in localized areas, the crushing action could be performed with less force.

U.S. Pat. No. 6,065,554 discloses a preform cutting element for a rotary drag-type drill bit comprises a front facing table of superhard material having a front surface, a peripheral surface, a rear surface bonded to a substrate of less hard material, and a cutting edge formed by at least part of the junction between the front surface and the peripheral surface. The front surface of the facing table is formed with a chip-breaking formation which is located adjacent the cutting edge and is shaped to deflect transversely of the front surface of the facing table cuttings which, in use, are removed by the cutting edge from the formation being drilled. The chip-breaking formation may comprise a peripheral groove or rebate, or an upstanding ridge or insert.

U.S. Pat. No. 7,762,359 discloses a cutter assembly including a rotatable cutting element, a rotary drill bit that may employ such a cutter assembly, and a method of fabricating a cutter assembly are disclosed. The cutter assembly includes a housing including a recess. A cutting element may be received by and rotatable within the recess of the housing. The cutting element includes a substrate and a superabrasive table that is attached to the substrate. At least one of the substrate and the superabrasive table includes surface features configured to promote rotation of the cutting element within the housing during cutting.

U.S. Pat. No. 2018/0318962 discloses a method for making a polycrystalline diamond compact (PDC). The method includes: 1) preparing a workblank of a polycrystalline diamond compact (PDC); and 2) thermally- or cold-etching the curved surface of the workblank of the polycrystalline diamond compact (PDC) using laser. The thermally- or cold-etching the curved surface of the workblank of the polycrystalline diamond compact (PDC) includes: employing a laser generator to produce a laser beam, expanding the laser beam, focusing the laser beam, to yield an energy concentration area on the surface of the workblank of the polycrystalline diamond compact, and etching the curved surface using the energy concentration area.

US 2018/0320450 discloses cutting elements for earth-boring tools including a substrate and a polycrystalline, superabrasive material secured to an end of the substrate. The polycrystalline superabrasive material may include a first transition surface extending in a direction oblique to a central axis of the substrate, a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction, and a curved, stress-reduction feature located on the second transition surface.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a spirally and/or radially serrated superhard cutter. In one embodiment, a cutter for use with a drill bit includes: a substrate for mounting in a pocket of the drill bit and made from a cermet material; and a cutting table made from a polycrystalline superhard material, mounted to the substrate at an interface, having a working face opposite from the interface, and having at least four serrations formed in the working face and a side thereof. Each serration has a pair of base edges and an apical edge extending above the base edges at the side of the cutting table. Each edge extends radially or spirally from the side of the cutting table to a central portion of the working face. The edges all converge at the center of the working face.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIGS. 1A-1D illustrate manufacture of a radially serrated superhard cutter, according to one embodiment of the present disclosure.

FIGS. 2A-2E illustrate the finished shaped cutter.

FIG. 3A illustrates brazing the shaped cutter into a blade of a drill bit. FIG. 3B illustrates the drill bit. FIG. 3C illustrates cutting action of the drill bit.

FIGS. 4A and 4B illustrates an alternative shaped cutter having rounded serrations, according to another embodiment of the present disclosure. FIG. 4C illustrates a second alternative shaped cutter having a knob for orientation or indexing thereof.

FIG. 5A illustrates a third alternative shaped cutter having spiral serrations, according to another embodiment of the present disclosure. FIG. 5B illustrates a fourth alternative shaped cutter having radial-spiral serrations, according to another embodiment of the present disclosure. FIGS. 5C and 5D illustrate a fifth alternative shaped cutter having radial serrations and a recessed central portion, according to another embodiment of the present disclosure.

FIGS. 6A and 6B illustrate a sixth alternative shaped cutter having radial serrations and a central chip-breaker, according to another embodiment of the present disclosure. FIGS. 6C and 6D illustrate a seventh alternative shaped cutter having radial serrations and a serrated chip-breaker, according to another embodiment of the present disclosure.

FIGS. 7A and 7B illustrate an eighth alternative shaped cutter having radial serrations and a serrated chip-breaker with a recessed inner portion, according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1A-1D illustrate manufacture of a radially serrated superhard cutter 1 (FIG. 2A), according to one embodiment of the present disclosure. Referring to FIG. 1A, the manufacturing process may commence by placement of a shear cutter 2 into a laser cutter machine 3. The shear cutter 2 may include a cylindrical cutting table 4 mounted to a cylindrical substrate 5. The cutting table 4 and substrate 5 may be circular-cylindrical (shown) or elliptic-cylindrical (not shown). The cutting table 4 may be made from a superhard material, such as polycrystalline diamond (PCD), and the substrate may be made from a hard material, such as a cermet, thereby forming a compact, such as a polycrystalline diamond compact. The cermet may be a cemented carbide, such as a group VIIIB metal-tungsten carbide. The group VIIIB metal may be cobalt. The shear cutter 2 may be manufactured by a high pressure, high temperature (HPHT) sintering operation using either a belt press or a cubic press.

Referring to FIG. 1B, the laser cutter machine 3 may be operated to remove selected PCD material from the cutting table 4 until serrations 6 are formed therein 4 a. Referring to FIG. 1C, the cutter 2 a may be repositioned in the laser cutting machine 3 and the machine operated remove selected cermet material from the substrate 5 until a keyway 7 is formed therein 5 a for indexing the spikes 2 when mounting the cutter 1 in a drill bit 8 (FIG. 3B). The keyway 7 may be located at an edge of the substrate 5 a and may extend from a back face thereof along a portion of a side thereof. The keyway 7 may be a slot inclined relative to a longitudinal axis of the cutter 1 by an angle ranging between ten and seventy degrees. The slot may have a width corresponding to a diameter of a mating key (not shown) formed in a cutter pocket of the drill bit 8. The keyway 7 may be angularly offset from a corresponding one of the serrations 6, such as being located opposite therefrom. The laser cutting machine 3 may be operated to form a plurality of the keyways 7 around the substrate 5 a, such as three keyways spaced at one-hundred twenty degree intervals. The laser cutting machine 3 may also be operated to form a chamfer in the back face of the substrate 5 a.

Alternatively, the serrations 6 may be formed by using an electrical discharge machine (EDM) instead of the laser cutting machine 3. Alternatively, the keyway 7 and the chamfer may be formed by the EDM or by grinding.

FIG. 1D illustrates leaching of the cutter 2 a. The cutter 2 a may be removed from the laser cutting machine 3. A portion of the substrate 5 a and a portion of the cutting table 4 a adjacent to the substrate may be masked 9. A portion of the cutter 2 a including the cutting table 4 a and the masked portion of the substrate 5 a may then be submerged into a bath of acid 10, such as Aqua regia, and left therein for a soaking time. The soaking time may be sufficient for the acid 10 to leach at least a substantial portion of catalyst from the exposed portion of the leached cutting table 4 b. The acid 10 may penetrate into a working face 11 w and a side 11 s of the cutting table 4 b, thereby increasing a thermal stability thereof. The working face 11 w may be opposite to an interface 11 e between the substrate 5 a and the cutting table 4 b. The interface 11 e may be planar (shown) or non-planar (not shown). The catalyst may be the same group VIIIB metal as the substrate 5.

FIGS. 2A-2E illustrate the finished shaped cutter 1. The cutting table 4 b may include a plurality of the serrations 6 (twelve shown) formed in the working face 11 w thereof. The number of serrations 6 may range between four and forty. Each serration 6 may have a triangular front face, such as isosceles, forming a portion of the side 11 s of the cutting table 4 c. At the side 11 s of the cutting table 4 b, each serration 6 may have a pair of base edges 6 b recessed relative to a center 11 c of the working face 11 w and an apical edge 6 a extending above the base edges. Each apical edge 6 a may have a maximum height 6 h above the respective base edges 6 b at the side 11 s of the cutting table 4 b. Each apical edge 6 a may extend radially from the side of the cutting table 4 b to the center 11 c of the working face 11 w. The maximum height 6 h of each apical edge 6 a may range between one-tenth of a millimeter and one millimeter. Each apical edge 6 a may be sharp.

Each pair of base edges 6 b may extend radially and vertically from the side 11 s of the cutting table 4 b to the center 11 c of the working face 11 w, thereby converging toward the respective apical edge 6 a as the respective serration 6 extends from the side 11 s, across the working face 11 w, and to the center 11 c thereof. The edges 6 a,b may all converge at the center 11 c of the working face 11 w. Accordingly, each serration 6 may have a maximum width at the side 11 s of the cutting table 4 b. The maximum width may be equal to the circumference of the side 11 s of the cutting table 4 b divided by the number of serrations 6. The apical edge 6 a and the converging base edges 6 b may result in each serration 6 having triangular, such as isosceles, side faces. An apical angle 6 g of each serration 6 may range between one-hundred degrees and one-hundred seventy degrees.

The serrations 6 may extend around an entirety of the side 11 s of the cutting table 4 b. The serrations 6 may be contiguous: each serration may share the base edges 6 b with adjacent serrations. Each serration 6 may be alike to the rest of the serrations. The center 11 c of the working face 11 w may be coplanar with the apical edges 6 a of the serrations 6. The serrations 6 may be symmetrically arranged about the cutting table 4 b.

Alternatively, the center 11 c of the working face 11 w may be coplanar with the base edges 6 b of the serrations 6 instead of the apical edges 6 a. Alternatively, the center 11 c of the of the working face 11 w may be at a height between heights of the base edges 6 b and the apical edges 6 a at the side 11 s of the cutting table 4 b. Alternatively, the serrations 6 may have a chamfer formed therein at a peripheral edge thereof between the side 11 s of the cutting table 4 b and the working face 11 w thereof.

FIG. 3A illustrates brazing the shaped cutter 1 into a blade 12 of the drill bit 8. The brazing operation may be manual or automated. A plurality of the cutters 1 may be mounted into pockets formed in a leading edge of the blade 12. Each shaped cutter 1 may be delivered to the pocket by an articulator 13. The articulator 13 may retain the cutter 1 only partially in the pocket such that the keyway 7 and key do not engage. Once delivered, a brazing material 14 may be applied to an interface formed between the respective pocket and the shaped cutter 1 using an applicator 15. As the brazing material 14 is being applied to the interface, the articulator 13 may rotate the shaped cutter 1 relative to the pocket to distribute the brazing material 14 throughout the interface.

A heater (not shown) may be operated to melt the brazing material 14. Cooling and solidification of the brazing material 14 may mount the shaped cutter 1 to the blade 12. The brazing operation may then be repeated for mounting additional shaped cutters 1 into additional pockets formed along the leading edge of the blade 12. The pocket may be inclined relative to a bottom face of the blade 12 adjacent thereto by a back rake angle 16 (FIG. 3C).

The keyways 7 may be used to index the cutters 1 for extending the service life thereof. Upon retrieval of the drill bit 8 from the wellbore, the drill bit may be inspected for wear. Should a wear flat be observed on any of the cutters 1, the worn cutter may be de-brazed from the respective cutter pocket and one of the other keyways 7 may be aligned and engaged with the respective key during re-brazing, thereby extending the service life of the cutters 1.

For cutters with a fewer number of serrations 6, such as less than or equal to eight serrations, the substrates thereof may have a keyway 7 for each serration and each keyway may be aligned opposite from a respective apical edge 6 a. The articulator 13 may then be operated to align one of the keyways 9 with the key and engage the aligned members, thereby ensuring that the shaped cutter is properly oriented to the operative position. The operative position may be where one of the apical edges 6 a of is perpendicular to a projection (not shown) of the leading edge of the respective blade 12 through the leading cutter pocket.

FIG. 3B illustrates the drill bit 8. The drill bit 8 may include a bit body 17, a shank 18, a cutting face, and a gage section 19. A lower portion of the bit body 17 adjacent to the cutting face may be made from a composite material, such as a ceramic and/or cermet body powder infiltrated by a metallic binder and an upper portion of the bit body adjacent to the shank 18 may be made from a softer material than the composite material of the upper portion, such as a metal or alloy shoulder powder infiltrated by the metallic binder. The bit body 17 may be mounted to the shank 18 during molding thereof. The shank 18 may be tubular and made from a metal or alloy, such as steel, and have a coupling, such as a threaded pin, formed at an upper end thereof for connection of the drill bit 8 to a drill collar (not shown). The shank 18 may have a flow bore formed therethrough and the flow bore may extend into the bit body 17 to a plenum thereof. The cutting face may form a lower end of the drill bit 8 and the gage section 19 may form an outer portion thereof.

Alternatively, the bit body 17 may be metallic, such as being made from steel, and may be hardfaced. The metallic bit body may be connected to a modified shank by threaded couplings and then secured by a weld or the metallic bit body may be monoblock having an integral body and shank.

The cutting face may include one or more primary blades 12 p, one or more secondary blades 12 s, fluid courses formed between the blades, the leading cutters 1, and backup cutters 5. The cutting face may have one or more sections, such as an inner cone, an outer shoulder, and an intermediate nose between the cone and the shoulder sections. The blades 12 may be disposed around the cutting face and each blade may be formed during molding of the bit body 17 and may protrude from a bottom of the bit body. The primary blades 12 p and the secondary blades 12 s may be arranged about the cutting face in an alternating fashion. The primary blades 12 p may each extend from a center of the cutting face, across the cone and nose sections, along the shoulder section, and to the gage section 19. The secondary blades 12 s may each extend from a periphery of the cone section, across the nose section, along the shoulder section, and to the gage section 19.

Each blade 12 may extend generally radially across the cone (primary only) and nose sections with a slight spiral curvature and along the shoulder section generally longitudinally with a slight helical curvature. Each blade 12 may be made from the same material as the bit body 17. The leading cutters 1 may be mounted into the pockets along leading edges of the blades 12 and the backup cutters 2 may be mounted into pockets adjacent to trailing edges of the blades. The backup cutters 2 may be omitted from the cone sections of the primary blades 12 p. One of the leading cutters in each blade 12 adjacent to the gage section 19 may be the shear cutter 2 (shown) or the shaped cutter 1 (not shown).

One or more ports 20 may be formed in the bit body 17 and each port may extend from the plenum and through the bottom of the bit body to discharge drilling fluid (not shown) along the fluid courses. Once the cutters 1 have been mounted to the respective blades 12, a nozzle (not shown) may be inserted into each port 20 and mounted to the bit body 17, such as by screwing the nozzle therein.

The gage section 19 may define a gage diameter of the drill bit 8. The gage section 19 may include a plurality of gage pads, such as one gage pad for each blade 12 and junk slots formed between the gage pads. The junk slots may be in fluid communication with the fluid courses formed between the blades 12. The gage pads may be disposed around the gage section 19 and each pad may be formed during molding of the bit body 17 and may protrude from the outer portion of the bit body. Each gage pad may be made from the same material as the bit body 17 and each gage pad may be formed integrally with a respective blade 12. Each gage pad may extend upward from a shoulder portion of the respective blade 12 to an exposed outer surface of the shank 18.

FIG. 3C illustrates cutting action of the drill bit 8. In use (not shown), the drill bit 8 may be assembled with one or more drill collars, such as by threaded couplings, thereby forming a bottomhole assembly (BHA). The BHA may be connected to a bottom of a pipe string, such as drill pipe or coiled tubing, thereby forming a drill string. The BHA may further include a steering tool, such as a bent sub or rotary steering tool, for drilling a deviated portion of the wellbore. The pipe string may be used to deploy the BHA into the wellbore. The drill bit 8 may be rotated, such as by rotation of the drill string from a rig (not shown) and/or by a drilling motor (not shown) of the BHA, while drilling fluid, such as mud, may be pumped down the drill string. A portion of the weight of the drill string may be set on the drill bit 8. The drilling fluid may be discharged by the nozzles and carry cuttings up an annulus formed between the drill string and the wellbore and/or between the drill string and a casing string and/or liner string.

As the drill bit 8 engages the rock formation 21 adjacent to the wellbore, each leading cutter 1 may gouge and/or crush 22 the formation, thereby facilitating subsequent shear cutting by the respective backup cutter 2. Additionally, the increased surface area of the cutting tables 4 b created by the serrations 6 improves heat transfer from the cutters 1 to the drilling fluid, thereby decreasing temperature of the cutting tables and extending service life of the cutters 1. Further, the serrations 6 break the cuttings before long chips can form and induce turbulent flow between the drilling fluid and the cutting tables 4 b, thereby further enhancing cooling of the cutting tables.

FIGS. 4A and 4B illustrates an alternative shaped cutter having rounded serrations 23, according to another embodiment of the present disclosure. The alternative cutter may include an alternative cutting table 24 mounted to the substrate 5 a (not shown). The alternative cutter may be manufactured in a similar fashion to the shaped cutter 1, discussed above.

The alternative cutting table 24 may include a plurality of serrations 23 (twenty shown) formed in a working face thereof. The number of serrations 23 may range between four and forty. Each serration 23 may have a triangular front face, such as isosceles, forming a portion of a side of the alternative cutting table 24. At the side of the alternative cutting table 24, each serration 23 may have a pair of base edges 23 b recessed relative to a center 24 c of the working face and an apical edge 23 a extending above the base edges. Each apical edge 23 a may have a maximum height above the respective base edges 23 b at the side of the alternative cutting table 24. Each apical edge 23 a may extend radially from the side of the alternative cutting table 24 to the center 24 c of the working face. The maximum height of each apical edge 23 a may range between one-tenth of a millimeter and one millimeter. Each apical edge 23 a may be rounded at the side of the alternative cutting table 24 and the round may be constant therefor until the apical edge reaches a convergence zone adjacent to the center 24 c of the working face.

Each pair of base edges 23 b may extend radially and vertically from the side of the alternative cutting table 24 to the center 24 c of the working face, thereby converging toward the respective apical edge 23 a as the respective serration 23 extends from the side, across the working face, and to the center 24 c thereof. The edges 23 a,b may all converge at the center 24 c of the working face. Accordingly, each serration 23 may have a maximum width 23 w at the side of the alternative cutting table 24. The maximum width 23 w may be equal to the circumference of the side of the alternative cutting table 24 divided by the number of serrations 23. Each round apical edge 23 a may have a radius 23 r ranging between one-eighth and three-fourths of the maximum width 23 w of the respective serration 23. The apical edge 23 a and the converging base edges 23 b may result in each serration 23 having triangular, such as isosceles, side faces. An apical angle of each serration 23 may range between one-hundred degrees and one-hundred seventy degrees.

The serrations 23 may extend around an entirety of the side of the alternative cutting table 24. The serrations 23 may be contiguous: each serration may share the base edges 23 b with adjacent serrations. Each serration 23 may be alike to the rest of the serrations. The center 24 c of the working face may be coplanar with midpoints of the apical edges 23 a of the serrations 23. The serrations 23 may be symmetrically arranged about the alternative cutting table 24. The serrations 23 may have a chamfer 23 c formed therein at a peripheral edge thereof between the side of the alternative cutting table 24 and the working face thereof.

Alternatively, each apical edge 23 a may be slightly truncated to form a flat and the flat may have a width equal to one-half of the radius 23 r. Alternatively, each apical edge 23 a may be sharp. Alternatively, the center 24 c of the of the working face may be coplanar with the base edges 23 b of the serrations 23 instead of the apical edges 23 a. Alternatively, the center 24 c of the of the working face may be at a height between heights of the base edges 23 b and the apical edges 23 a at the side of the alternative cutting table 24.

FIG. 4C illustrates a second alternative cutter 25 having a knob 26 for orientation or indexing thereof. The second alternative cutter 25 may include either the cutting table 4 b (shown) or the alternative cutting table 24 (not shown) mounted to an alternative substrate 27. The alternative substrate 27 may have a plurality of knobs 26 mounted to a back face 27 b thereof for orienting (one knob for each serration 6) or indexing (three knobs at one-hundred twenty degree intervals) the serrations. The alternative substrate 27 may be similar to the substrate 5 a except for having the knobs 26 mounted thereto instead of the keyway 7 formed therein. The knob 26 may be formed separately from the rest of the second alternative cutter 25 and then mounted to the alternative substrate 27 thereof, such as by brazing. The alternative substrate 27 may be angularly offset from the corresponding serration 6, such as being located opposite therefrom (one-hundred eighty degrees therefrom). The knob 26 may be hemi-spherical and have a diameter ranging between twenty-five and forty-five percent of a diameter of the back face 27 b. Instead of a key, the drill bit 8 may have a dimple (not shown) formed in the cutter pocket thereof for mating with the knob 26. The knob 26 may be made from the same material as the substrate or a different material than the substrate, such as a metal or alloy, such as steel.

Alternatively, the knob 26 may be formed integrally with the alternative substrate 27.

FIG. 5A illustrates a third alternative shaped cutter having spiral serrations 28, according to another embodiment of the present disclosure. The alternative cutter may include an alternative cutting table 29 mounted to the substrate 5 a (not shown). The third alternative cutter may be manufactured in a similar fashion to the shaped cutter 1, discussed above.

The alternative cutting table 29 may include a plurality of serrations 28 (twenty shown) formed in a working face thereof. The number of serrations 28 may range between four and forty. Each serration 28 may have a triangular front face, such as isosceles, forming a portion of a side of the alternative cutting table 29. At the side of the alternative cutting table 29, each serration 28 may have a pair of base edges 28 b recessed relative to a center 29 c of the working face and an apical edge 28 a extending above the base edges. Each apical edge 28 a may have a maximum height above the respective base edges 28 b at the side of the alternative cutting table 29. Each apical edge 28 a may extend spirally from the side of the alternative cutting table 29 to the center 29 c of the working face. The maximum height of each apical edge 28 a may range between one-tenth of a millimeter and one millimeter. Each apical edge 28 a may be sharp.

Each pair of base edges 28 b may extend spirally and vertically from the side of the alternative cutting table 29 to the center 29 c of the working face, thereby converging toward the respective apical edge 28 a as the respective serration 28 extends from the side, across the working face, and to the center 29 c thereof. The edges 28 a,b may all converge at the center 29 c of the working face. Accordingly, each serration 28 may have a maximum width at the side of the alternative cutting table 29. The maximum width may be equal to the circumference of the side of the alternative cutting table 29 divided by the number of serrations 28. An apical angle of each serration 28 may range between one-hundred degrees and one-hundred seventy degrees.

The serrations 28 may extend around an entirety of the side of the alternative cutting table 29. The serrations 28 may be contiguous: each serration may share the base edges 28 b with adjacent serrations. Each serration 28 may be alike to the rest of the serrations. The center 29 c of the working face may be coplanar with the apical edges 28 a of the serrations 28. The serrations 28 may have a chamfer 28 c formed therein at a peripheral edge thereof between the side of the alternative cutting table 29 and the working face thereof. The serrations 28 may spiral in a clockwise direction from the side of the alternative cutting table 29 to the center 29 c of the working face.

Alternatively, the serrations 28 may spiral in a counter-clockwise direction from the side of the alternative cutting table 29 to the center 29 c of the working face. Alternatively, each apical edge 28 a may be rounded at the side of the alternative cutting table 29 and the round may be constant therefor until the apical edge reaches a convergence zone adjacent to the center 29 c of the working face. Each round apical edge may have a radius ranging between one-eighth and three-fourths of the maximum width of the respective serration 28. Alternatively, each apical edge 28 a may be slightly truncated to form a flat and the flat may have a width equal to one-half of the radius. Alternatively, the center 29 c of the of the working face may be coplanar with the base edges 28 b of the serrations 28 instead of the apical edges 28 a. Alternatively, the center 29 c of the of the working face may be at a height between heights of the base edges 28 b and the apical edges 28 a at the side of the alternative cutting table 29.

FIG. 5B illustrates a fourth alternative shaped cutter having radial-spiral serrations 30, according to another embodiment of the present disclosure. The alternative cutter may include an alternative cutting table 31 mounted to the substrate 5 a (not shown). The fourth alternative cutter may be manufactured in a similar fashion to the shaped cutter 1, discussed above.

The alternative cutting table 31 may include a plurality of serrations 30 (twenty shown) formed in a working face thereof. Each serration 30 may have an outer spiral portion 30 s and an inner radial portion 30 r connected at a junction 30 j thereof. Each junction 30 j may be staggered relative to junctions of adjacent serrations 30. The number of serrations 30 may range between four and forty. Each serration 30 may have a triangular front face, such as isosceles, forming a portion of a side of the alternative cutting table 31. At the side of the alternative cutting table 31, each serration 30 may have a pair of base edges 30 b recessed relative to a center 31 c of the working face and an apical edge 30 a extending above the base edges. Each apical edge 30 a may have a maximum height above the respective base edges 30 b at the side of the alternative cutting table 31. Each apical edge 30 a may extend spirally for the outer portion 30 s thereof and radially for the inner portion 30 r thereof from the side of the alternative cutting table 31 to the center 31 c of the working face. The maximum height of each apical edge 30 a may range between one-tenth of a millimeter and one millimeter. Each apical edge 30 a may be sharp.

Each pair of base edges 30 b may extend vertically and spirally for the outer portion 30 s thereof and radially for the inner portion 30 r thereof from the side of the alternative cutting table 31 to the center 31 c of the working face, thereby converging toward the respective apical edge 30 a as the respective serration 30 extends from the side, across the working face, and to the center 29 c thereof. The edges 30 a,b may all converge at the center 31 c of the working face. Accordingly, each serration 30 may have a maximum width at the side of the alternative cutting table 31. The maximum width may be equal to the circumference of the side of the alternative cutting table 31 divided by the number of serrations 30. An apical angle of each serration 30 may range between one-hundred degrees and one-hundred seventy degrees.

The serrations 30 may extend around an entirety of the side of the alternative cutting table 31. The serrations 30 may be contiguous: each serration may share the base edges 30 b with adjacent serrations. Each serration 30 may be alike to the rest of the serrations. The center 31 c of the working face may be coplanar with the apical edges 30 a of the serrations 30. The serrations 30 may each have a chamfer 30 c formed therein at a peripheral edge thereof between the side of the alternative cutting table 3 and the working face thereof. The outer portions 30 s of the serrations 30 may spiral in a counter-clockwise direction from the side of the alternative cutting table 31 to the junction 30 j.

Alternatively, the outer portions 30 s of the serrations 30 may spiral in a clockwise direction from the side of the alternative cutting table 29 to the junction 30 j. Alternatively, the outer portions 30 s of the serrations 30 may be radial and the inner portions 30 r of the serrations may be spiral. Alternatively, each apical edge 30 a may be rounded at the side of the alternative cutting table 31 and the round may be constant therefor until the apical edge reaches a convergence zone adjacent to the center 31 c of the working face. Each round apical edge may have a radius ranging between one-eighth and three-fourths of the maximum width of the respective serration 30. Alternatively, each apical edge 30 a may be slightly truncated to form a flat and the flat may have a width equal to one-half of the radius. Alternatively, the center 31 c of the of the working face may be coplanar with the base edges 30 b of the serrations 30 instead of the apical edges 30 a. Alternatively, the center 31 c of the of the working face may be at a height between heights of the base edges 30 b and the apical edges 30 a at the side of the alternative cutting table 31.

FIGS. 5C and 5D illustrate a fifth alternative shaped cutter having radial serrations 33 and a recessed central portion 32 c, according to another embodiment of the present disclosure. The alternative cutter may include an alternative cutting table 32 mounted to the substrate 5 a. The alternative cutter may be manufactured in a similar fashion to the shaped cutter 1, discussed above.

The alternative cutting table 32 may include a plurality of serrations 33 (twenty shown) formed in a working face thereof and the central portion 32 c of the working face may be recessed relative to the side thereof. The number of serrations 33 may range between four and forty. Each serration 33 may have a triangular front face, such as isosceles, forming a portion of a side of the alternative cutting table 32. At the side of the alternative cutting table 32, each serration 33 may have a pair of base edges 33 b raised relative to a central portion 32 c of the working face and an apical edge 33 a extending above the base edges. Each apical edge 33 a may have a maximum height above the respective base edges 33 b at the side of the alternative cutting table 32. Each apical edge 33 a may extend radially and vertically from the side of the alternative cutting table 32 to a periphery of the central portion 32 c of the working face. A first maximum height of each apical edge 33 a above the respective base edges 33 b may range between one-tenth of a millimeter and one millimeter. A second maximum height of each apical edge 33 a above the central portion 32 c may be greater than the first maximum height, such as one point five times or two times the first maximum height. Each apical edge 33 a may be sharp.

Each pair of base edges 33 b may extend radially and vertically from the side of the alternative cutting table 32 to the periphery of the central portion 32 c of the working face, thereby converging toward the respective apical edge 33 a as the respective serration 33 extends from the side, across the working face, and to the periphery of the central portion 32 c thereof. Accordingly, each serration 33 may have a maximum width at the side of the alternative cutting table 32. The maximum width may be equal to the circumference of the side of the alternative cutting table 32 divided by the number of serrations 33. The apical edge 33 a and the converging base edges 33 b may result in each serration 33 having triangular, such as isosceles, side faces. An apical angle of each serration 33 may range between one-hundred degrees and one-hundred seventy degrees.

The serrations 33 may extend around an entirety of the side of the alternative cutting table 32. The serrations 33 may be contiguous: each serration may share the base edges 33 b with adjacent serrations. Each serration 33 may be alike to the rest of the serrations. The serrations 33 may be symmetrically arranged about the alternative cutting table 32. The serrations 33 may have a chamfer 33 c formed therein at a peripheral edge thereof between the side of the alternative cutting table 32 and the working face thereof. Each apical edge 33 a may descend linearly toward the central portion 32 c at an inclination angle ranging between five and forty-five degrees. The serrations 33 may not fully converge at the periphery of the central portion 32 c, thereby imparting a jagged shape thereto. The central portion 32 c may be planar and have a diameter ranging between five percent and thirty percent of a diameter of the alternative cutting table 32.

Alternatively, outer portions of the serrations 33 may spiral in a clockwise or counter-clockwise direction from the side of the alternative cutting table 32 to a junction located between the side and the periphery of the central portion 32 c. Alternatively, the outer portions of the serrations 33 may be radial and inner portions of the serrations may be spiral. Alternatively, the serrations 33 may spiral in a clockwise or counter-clockwise direction from the side of the alternative cutting table 32 to the periphery of the central portion 32 c of the working face. Alternatively, each apical edge 33 a may be rounded at the side of the alternative cutting table 32 and the round may be constant therefor until the apical edge reaches the periphery of the central portion 32 c. Each round apical edge may have a radius ranging between one-eighth and three-fourths of the maximum width of the respective serration 33. Alternatively, each apical edge 33 a may be slightly truncated to form a flat and the flat may have a width equal to one-half of the radius.

FIGS. 6A and 6B illustrate a sixth alternative shaped cutter having radial serrations 35 and a central chip-breaker 36, according to another embodiment of the present disclosure. The alternative cutter may include an alternative cutting table 34 mounted to the substrate 5 a. The alternative cutter may be manufactured in a similar fashion to the shaped cutter 1, discussed above.

The alternative cutting table 34 may include a plurality of serrations 35 (twenty shown) formed in a working face thereof and the chip-breaker 36 formed in a central portion of the working face recessed relative to the side thereof. The number of serrations 35 may range between four and forty. Each serration 35 may have a triangular front face, such as isosceles, forming a portion of a side of the alternative cutting table 34. At the side of the alternative cutting table 34, each serration 35 may have a pair of base edges 35 b raised relative to at least a periphery of the chip-breaker 36 and an apical edge 35 a extending above the base edges. Each apical edge 35 a may have a maximum height above the respective base edges 35 b at the side of the alternative cutting table 34. Each apical edge 35 a may extend radially and vertically from the side of the alternative cutting table 34 to the periphery of the chip-breaker 36. A first maximum height of each apical edge 35 a above the respective base edges 35 b may range between one-tenth of a millimeter and one millimeter. A second maximum height of each apical edge 35 a above the periphery of the chip-breaker 36 may be greater than the first maximum height, such as one point five times or two times the first maximum height. Each apical edge 35 a may be sharp.

Each pair of base edges 35 b may extend radially and vertically from the side of the alternative cutting table 34 to the periphery of the chip-breaker 36, thereby converging toward the respective apical edge 35 a as the respective serration 35 extends from the side, across the working face, and to the periphery of the chip-breaker. Accordingly, each serration 35 may have a maximum width at the side of the alternative cutting table 34. The maximum width may be equal to the circumference of the side of the alternative cutting table 34 divided by the number of serrations 35. The apical edge 35 a and the converging base edges 35 b may result in each serration 35 having rhomboidal side faces. An apical angle of each serration 35 may range between one-hundred degrees and one-hundred seventy degrees.

The serrations 35 may extend around an entirety of the side of the alternative cutting table 34. The serrations 35 may be contiguous: each serration may share the base edges 35 b with adjacent serrations. Each serration 35 may be alike to the rest of the serrations. The serrations 35 may be symmetrically arranged about the alternative cutting table 34. The serrations 35 may have a chamfer 35 c formed therein at a peripheral edge thereof between the side of the alternative cutting table 24 and the working face thereof. Each apical edge 33 a may descend linearly toward the chip-breaker 36 at an inclination angle ranging between five and forty-five degrees. The serrations 35 may not fully converge at the periphery of the chip-breaker 36, thereby imparting a jagged shape thereto. The chip-breaker 36 may have a planar inner portion and have a diameter ranging between one-third and two-thirds of a diameter of the alternative cutting table 34. The inner portion of the chip-breaker 36 may be raised above the periphery thereof and the chip-breaker may have a chamfer formed between the inner portion and the periphery. The periphery of the chip-breaker 36 may be non-planar and may increase in height from a portion thereof adjacent to the serrations 35 to a portion thereof adjacent to the central portion.

Alternatively, outer portions of the serrations 35 may spiral in a clockwise or counter-clockwise direction from the side of the alternative cutting table 34 to a junction located between the side and the periphery of the chip-breaker 36. Alternatively, the outer portions of the serrations 35 may be radial and inner portions of the serrations may be spiral. Alternatively, the serrations 35 may spiral in a clockwise or counter-clockwise direction from the side of the alternative cutting table 34 to the periphery of the chip-breaker 36. Alternatively, each apical edge 35 a may be rounded at the side of the alternative cutting table 34 and the round may be constant therefor until the apical edge reaches the periphery of the chip-breaker 36. Each round apical edge may have a radius ranging between one-eighth and three-fourths of the maximum width of the respective serration 35. Alternatively, each apical edge 35 a may be slightly truncated to form a flat and the flat may have a width equal to one-half of the radius.

FIGS. 6C and 6D illustrate a seventh alternative shaped cutter having radial serrations 35 and a serrated chip-breaker 37, according to another embodiment of the present disclosure. The seventh alternative shaped cutter may be similar to the sixth alternative shaped cutter except for having a modified chip-breaker 37. The modified chip-breaker 37 may have an inner set of serrations 37 s formed in the inner portion thereof. The modified chip-breaker 37 may have one inner serration 37 s for each (outer) serration 35 and the inner serrations may be aligned with the outer serrations. The inner serrations 37 s may have apical edges coplanar with a center 37 c of the modified chip-breaker 37.

FIGS. 7A and 7B illustrate an eighth alternative shaped cutter having radial serrations 35 and a serrated chip-breaker 38 with a recessed inner portion 38 n, according to another embodiment of the present disclosure. The eighth alternative shaped cutter may be similar to the seventh alternative shaped cutter except for having a modified chip-breaker 38. The modified chip-breaker 38 may have an inner set of serrations 38 s formed in an intermediate portion thereof and extending from a periphery thereof to an inner portion 38 n which is recessed relative to the periphery. The modified chip-breaker 38 may have one inner serration 38 s for each (outer) serration 35 and the inner serrations may be aligned with the outer serrations 35. The inner serrations 38 s may have apical edges and base edges raised above the recessed inner portion 38 n of the modified chip-breaker 38. The apical edges and base edges of the inner serrations 38 s may extend radially and decline vertically from the periphery of the modified chip-breaker to the inner portion 38 n thereof.

Alternatively, outer portions of the inner serrations 38 s may spiral in a clockwise or counter-clockwise direction from the periphery of the modified chip-breaker 38 to a junction located between the periphery of the modified chip-breaker and the inner portion 38 n thereof. Alternatively, the outer portions of the inner serrations 38 s may be radial and inner portions of the inner serrations may be spiral. Alternatively, the inner serrations 38 s may spiral in a clockwise or counter-clockwise direction from the periphery of the modified chip-breaker 38 to the inner portion 38 n thereof. Alternatively, each apical edge of the inner serrations 38 s may be rounded at the periphery of the modified chip-breaker 38 and the round may be constant therefor until the apical edge reaches the inner portion 38 n thereof. Each round apical edge may have a radius ranging between one-eighth and three-fourths of the maximum width of the respective inner serration 38 s. Alternatively, each apical edge of the inner serrations 38 s may be slightly truncated to form a flat and the flat may have a width equal to one-half of the radius.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow. 

1. A cutter for use with a drill bit, comprising: a substrate for mounting in a pocket of the drill bit and made from a cermet material; and a cutting table made from a polycrystalline superhard material, mounted to the substrate at an interface, having a working face opposite from the interface, and having at least four serrations formed in the working face and a side thereof, wherein: each serration has a pair of base edges and an apical edge extending above the base edges at the side of the cutting table, each edge extends radially or spirally from the side of the cutting table to a central portion of the working face, and the edges all converge at the center of the working face.
 2. The cutter of claim 1, wherein a maximum height of the apical edges relative to the respective base edges ranges between one-tenth of a millimeter and one millimeter.
 3. The cutter of claim 1, wherein an apical angle of each serration ranges between one-hundred degrees and one-hundred seventy degrees.
 4. The cutter of claim 1, wherein: each edge extends from the side of the cutting table to a center of the working face, and the apical edges are coplanar with the center of the working face.
 5. The cutter of claim 1, wherein: the cutting table has at least ten of the serrations, and the serrations extend around an entirety of the side of the cutting table.
 6. The cutter of claim 1, wherein each serration shares the base edges with adjacent serrations.
 7. The cutter of claim 1, wherein each serration has a triangular front face and triangular side faces.
 8. The cutter of claim 1, wherein the substrate has a keyway formed in an edge thereof for orienting or indexing the serrations.
 9. The cutter of claim 1, wherein each apical edge is sharp.
 10. The cutter of claim 1, wherein each apical edge is rounded and has a radius ranging between one-eighth and three-fourths of a maximum width of the respective serration.
 11. The cutter of claim 1, wherein the substrate has a bump formed in or mounted to a back face thereof for orienting or indexing the serrations.
 12. A bit for drilling a wellbore, comprising: a shank having a coupling formed at an upper end thereof; a body mounted to a lower end of the shank; and a cutting face forming a lower end of the bit and comprising: a blade protruding from the body; and the cutter of claim 1, wherein the substrate is mounted in the pocket formed in the blade.
 13. The bit of claim 12, wherein the cutting face further comprises a backup shear cutter mounted in a second pocket formed in the blade.
 14. The cutter of claim 1, wherein each edge extends radially from the side of the cutting table to a center of the working face.
 15. The cutter of claim 1, wherein each edge extends spirally from the side of the cutting table to a center of the working face.
 16. The cutter of claim 1, wherein each edge extends spirally for a first portion of the respective serration and radially for a second portion of the respective serration.
 17. The cutter of claim 16, wherein: each first portion and the respective second portion are connected at a respective junction, and each junction is staggered relative to junctions of adjacent serrations.
 18. The cutter of claim 1, wherein: the central portion of the working face is recessed relative to the side of the working face, and each edge extends radially or spirally and declines vertically from the side to the central portion of the working face.
 19. The cutter of claim 18, wherein: the apical edges have a first maximum height relative to the base edges and a second maximum height relative to the central portion, and the second maximum height is greater than the first maximum height.
 20. The cutter of claim 18, wherein each edge extends radially from the side of the cutting table to the central portion of the working face.
 21. The cutter of claim 18, wherein each edge extends spirally from the side of the cutting table to the central portion of the working face.
 22. The cutter of claim 18, wherein each edge extends spirally for a first portion of the respective serration and radially for a second portion of the respective serration.
 23. The cutter of claim 18, wherein the cutting table further has a chip-breaker formed in the central portion of the working face and having a jagged and non-planar periphery.
 24. The cutter of claim 23, wherein: the serrations are outer serrations, and the cutting table further has at least four inner serrations are formed in the chip-breaker.
 25. The cutter of claim 24, wherein: an inner portion of the chip-breaker is recessed relative to the periphery thereof, and the inner serrations extend radially and decline vertically from the periphery to the inner portion of the chip-breaker.
 26. The cutter of claim 25, wherein the inner serrations extend radially from the side of the cutting table to the inner portion of the chip-breaker.
 27. The cutter of claim 25, wherein the inner serrations extend spirally from the side of the cutting table to the inner portion of the chip-breaker.
 28. The cutter of claim 25, wherein the inner serrations extend spirally for a first portion thereof and radially for a second portion thereof. 